What Is Bokeh?

Bokeh is the look of the out-of-focus parts of a photograph: how smooth or restless the blur is, and what shape blurred points of light take. It matters because the blur often fills more of the frame than the subject does, so its character sets the mood of the picture as much as anything that is sharp.

Two different things hide under the word. The amount of blur is pure geometry, and you control it with the lens opening, the distances and the framing. The quality of the blur comes from how the lens was designed: whether a blurred light is a soft round glow, a disc with a hard bright rim, a hexagon or a lemon shape. This page gives you a simple way to predict the first and a way to see and judge the second.

The word comes from the Japanese boke, meaning blur or haze. In English it is usually said “BOH-kay” or “BOH-kuh”; the Japanese is closer to “BOH-keh.” People who have only heard it often search for “boca” or “bokah,” and they mean the same thing.

Shooting on a phone? Portrait mode explained shows how phone cameras fake bokeh with a depth map and where the illusion gives itself away.

Amount and character: the two halves of bokeh

Every point in the scene that is not at the focus distance reaches the sensor as a small patch of light instead of a point. Make the patches big and the background melts; keep them small and it stays readable. That is the amount. Now look inside one patch. Is it evenly lit, brighter in the middle and fading at the edge, or brighter at the rim like a ring? Is it round or many-sided? That is the character, and it is the part photographers argue about.

The two halves are independent. You can blur a background a great deal with a lens whose blur looks harsh, and you can get soft, pleasant blur in small amounts from a lens with a gentle rendering. The pair below shows the difference between blur that recedes and blur that competes with the subject.

Which photo has smoother, less distracting bokeh?

A B

Keep the two halves apart in your head and most of the confusion about bokeh goes away. When someone says a lens has “great bokeh” they may mean it blurs a lot (usually a wide aperture) or that its blur looks smooth (a design choice). Those are different claims.

How big the blur gets: the lens opening rule

Here is the simplest correct way to predict background blur. Take the focal length and divide it by the f-number. The answer, in millimeters, is the width of the lens opening as seen from the front, which optical designers call the entrance pupil. A light far behind your subject blurs into a disc that, measured at the subject, is about that wide.

An 85mm lens at f/1.8 has an opening of 85 ÷ 1.8 = 47 mm. So a distant streetlight behind a portrait sitter becomes a disc about 47 mm across at the sitter’s position, roughly a third the width of an adult face. A phone’s main camera, with a real focal length of about 7 mm at f/1.8, has an opening of about 4 mm: the same streetlight becomes a disc about the size of the pupil of the sitter’s eye. That is why the phone needs software to fake what the big lens does with glass.

To see what that means in a picture, compare the disc with the width of the frame. The table assumes a head and shoulders frame 60 cm wide at the subject and a background far away. You stand wherever each lens needs to give that framing.

Three things in that table surprise most people.

• A 200mm zoom at f/4 blurs a distant background slightly more than an 85mm at f/1.8. The f-number alone does not tell you the amount of blur. The physical size of the opening does, and a long lens at a modest f-number can have a big one.
• Sensor size does not appear in the sum. At the same framing, what matters is the opening. On a 1.5x crop sensor you use a 56mm to frame like an 85mm on full frame, and at the same f/1.8 its opening is 31 mm instead of 47 mm, about two thirds as much blur. To match the full frame look you would need f/1.2 (1.8 ÷ 1.5). Full frame vs crop sensor follows the same idea through depth of field and noise.
• A wide lens at a wide aperture still blurs little. A 24mm at f/1.4 has a smaller opening than a 50mm at f/1.8, so the background stays recognizable even wide open.

This is also where the idea of telephoto “compression” misleads. A long lens does not squeeze the background closer and blur it by doing so. Perspective, how big the background looks next to the subject, comes only from where you stand; lens compression explains why. What a long lens does for blur is give you a bigger opening at the same f-number, and because you stand farther back for the same framing, it shows a smaller slice of background, magnified, so fewer distractions and larger blobs fill the frame behind the subject.

Want the numbers for your own lens? The depth of field calculator gives the near and far limits of sharpness for any focal length, aperture and distance.

Background distance often beats another stop of aperture

The rule above is for a background far away. When the background is closer, the disc shrinks in proportion to how far the background sits behind the subject compared with how far it is from the camera. The multiplier is (background distance minus subject distance) divided by background distance, both measured from the camera.

Take an 85mm at f/1.8 with the subject 2 m from the camera:

Moving the sitter away from a wall, from 1 m in front of it to 10 m, makes the blur 2.5 times larger without touching the camera. Opening up one full stop makes the opening only 1.4 times larger, and two stops makes it 2 times larger. So walking your subject away from the background can be worth more than two stops of aperture, and it costs nothing. Notice too that the gain flattens out: past about 10 m, more distance adds little.

Your own distance to the subject matters as well, through framing. Step in close with the same lens and the subject fills the frame, so the same disc is a much larger share of the picture. That is why macro photography gives a melted background even at modest apertures.

Bokeh is not the same as depth of field

Depth of field is the zone in front of and behind the focus point that looks acceptably sharp. Bokeh is about what happens well outside that zone. The two are related, since both get stronger with a wider aperture and a closer subject, but they come apart in a way that matters.

Frame the same portrait with a 50mm and an 85mm at the same f-number, standing farther back with the 85mm. The depth of field around the face comes out almost the same, because the longer lens’s shallower focus is offset by the greater distance. The far background is not the same: the 85mm’s opening is 1.7 times wider, so its background blur is 1.7 times larger. Depth of field tells you how much of the subject is sharp; the opening rule tells you how soft the far background will be. A shallow depth of field is the tool, bokeh is the look it produces outside the zone of focus.

Wondering where “acceptably sharp” ends? Circle of confusion is the small blur size that the depth of field numbers are built on.

Try the numbers in the camera simulator

Set the simulator to its widest aperture and longest focal length, then change one thing at a time and watch the background: the f-number first, then the focal length, and see which moves the blur more.

Want other scenes to try this on? The full camera simulator has eight, and 21 challenges.

What gives blur its character

The size of the blur is geometry. Its look comes from the lens. Point lights are the best test because each one turns into a picture of how the lens spreads a single point, but the same behavior shapes leaves, branches and faces in the background, only less obviously.

The shape of the discs: wide open and stopped down

Wide open, the aperture blades in most lenses are pulled back out of the light path, and the opening is the round edge of the lens itself. Blurred lights are round. Stop down and the blades close into a polygon, and every blurred light takes that shape: six blades make hexagons, seven make heptagons, nine make nonagons that look nearly round. Blades with curved edges keep the opening close to a circle for the first stop or two. Blades change the outline of a disc, not how soft its inside is, so more blades do not make blur creamier, only rounder when you stop down.

Cat’s eyes and swirl near the edges

Toward the corners of the frame, round discs often become lemon or cat’s eye shapes. Light coming in at an angle is clipped by the front and back of the lens barrel, so the opening seen from the corner is the overlap of two circles. This is optical vignetting, and it is the same thing that darkens corners wide open. It is strongest at the widest aperture and shrinks as you stop down, which is why many lenses render rounder discs one stop down.

In some lenses the cat’s eyes line up around the center of the frame and, helped by a curved plane of focus, the whole background seems to rotate around the subject. That is swirly bokeh. Old portrait designs show it strongly, and it is one reason people adapt vintage lenses to modern cameras.

Smooth glow or bright rim

Look closely at a single blurred light. If it is brighter in the middle and fades softly at the edge, the blur will look smooth and recede. If it is darker in the middle with a bright ring at its rim, blurred edges in the background overlap as lines, and the background looks busy. The cause is spherical aberration, the way a lens focuses light through its edge slightly differently from light through its center. No real lens is perfect here, and designers choose which way to leave it.

The choice cuts both ways. A lens that renders the background as soft glows usually renders blurred foreground lights with bright rims, and the reverse. So the same lens can look smooth behind the subject and harsher in front of it. When people say a lens has creamy bokeh, they almost always mean its background.

Double lines in branches and grass

Bright-rimmed blur shows up most in fine, high-contrast lines such as twigs against the sky, grass or wire fences. Each line blurs into two faint parallel edges, and a tangle of branches turns into a nervous mesh. This is what people usually mean by busy bokeh. You can often fix it without changing lens: open up so the lines blur further, move so a plainer background sits behind the subject, or put more distance between subject and background.

Rings, fringes, donuts and bubbles

• Onion rings. Fine concentric rings inside each disc come from tiny surface ripples in molded aspherical elements. They show in bright point lights, rarely elsewhere.
• Colored fringes. Blurred edges in front of focus often take a magenta tint and those behind a green one. This is longitudinal chromatic aberration: the lens focuses colors at slightly different distances.
• Donuts. Mirror lenses have a central obstruction, so every blurred light becomes a ring with a hole in the middle.
• Soap bubbles. Some simple old designs render discs with an extremely bright, thin rim. It is the bright-rim effect taken to an extreme, and some photographers seek it out on purpose.
• Apodization. A few lenses carry a filter that darkens gradually toward the edge of the opening, deliberately softening every disc’s edge for the smoothest possible blur.

Reading a lens’s bokeh in five minutes

Specifications and reviews will not tell you how a lens looks behind your kind of subject. A quick test will.

1. At dusk, find a string of small lights or distant streetlights. Focus on something about 1 m away with the lights well behind it.
2. Shoot wide open, then one and two stops down. Look at a disc in the center and one in a corner at full size: round or polygon, even or rimmed, round or cat’s eye.
3. Now focus far and put the lights in front of the focus distance, close to the lens. Compare these foreground discs with the background ones.
4. In daylight, focus on something close with bare branches or grass behind it and look for double lines.

Ten frames tell you which aperture renders the background the way you like and which backgrounds that lens handles badly. How to test a lens covers sharpness and the other defects in the same session.

Strong background blur with the lens you already have

The opening rule shows why a kit lens can do more than people think. At 55mm and f/5.6 the opening is under 10 mm, but a telephoto zoom at 200mm and f/5.6 has an opening of 36 mm, about the same as a 50mm at f/1.4. So:

• Use the long end. Zoom all the way in and step back to frame. The opening grows with focal length.
• Open the aperture fully. In aperture priority mode set the lowest f-number and let the camera handle the shutter speed.
• Move the subject away from the background. Per the table above, this can be worth two stops.
• Get closer for tighter framing. A head fills more of the frame, so the same blur takes up more of the picture.
• Choose a background with small, distant highlights. Sunlit leaves, water glints or lights read as bokeh; a plain wall a meter behind reads as a wall.

A fast lens makes all of this easier and works in less light, but distances and focal length are free.

Lights at night and shaped bokeh

Night is the easiest time to see bokeh because small bright lights stand out from a dark background. Remember that a disc spreads a light over a larger area, so a bigger disc is dimmer; small, bright sources make the clearest discs. String lights a few meters behind the subject, a window of city lights beyond a nearby subject, or candles in the background all work. Focus on the subject, never the lights, and let the camera raise the ISO if it needs to. Night photography and photographing holiday lights cover the exposure side.

Shaped bokeh uses the fact that a blurred point takes the shape of the opening. Replace the opening with your own shape and every blurred light takes it.

1. Cut a disc of black card as wide as the front of the lens. A strip of card taped around its edge turns it into a cap that slips over the lens or hood.
2. Cut your shape in the center. It must be smaller than the lens opening at its widest aperture, or the round opening will still define the shape; about one centimeter across suits most fast normal lenses.
3. Tape the card over the front of the lens so the shape sits centered on the glass.
4. Set the widest aperture and focus on something close, with small lights well behind it. The farther out of focus the lights are, the larger and clearer the shapes.

The card blocks light, so expect a slower shutter speed or higher ISO. It makes a good photography project for a dark evening.

Bokeh added in editing or by a phone

Portrait mode and editing tools build blur from a depth map: a guess at how far away each part of the scene is. They work well on a clean subject against a distant background. They give themselves away where depth is hard to guess: stray hair, glasses, the gap between an arm and a body, and objects that should be partly blurred because they lean toward the camera. Real blur grows smoothly with distance from the focus plane; a depth map often has only a few steps.

Software works best to strengthen blur you already caught in camera. A small amount of extra background blur on a photo that already has separation is hard to spot; turning a sharp background into heavy blur rarely convinces. Lightroom masking shows how to select a background cleanly before softening it.

Common mistakes and misconceptions about bokeh

“Bokeh means background blur.” It means the character of the blur. Two photos can have the same amount of blur and very different bokeh.

“Only the f-number matters.” The opening is focal length divided by f-number, and the background distance multiplies it. A 200mm at f/4 blurs a distant background slightly more than an 85mm at f/1.8.

“Long lenses compress the background, and that is what blurs it.” Perspective comes from where you stand. Long lenses blur more because their opening is larger at the same f-number.

“More aperture blades mean creamier bokeh.” Blades only shape the discs once you stop down, and they change the outline, not the softness inside.

“Hexagons mean something is wrong.” They are a picture of the stopped-down aperture. Open up to get round discs.

Missing focus wide open. At f/1.4 close up, the sharp zone can be thinner than the distance from nose to eye. Use a single autofocus point on the nearer eye and check at full size.

Ignoring what is behind the subject. Blur does not delete things. A bright blob behind a head reads as a halo and a blurred red sign still pulls the eye. Move until the shapes and colors in the blur support the subject.

Blurring everything by habit. An environmental portrait, a street scene or a building often needs a readable background to tell the story. Selective focus is a choice, not a default.

Try this: the same subject, three ways to blur

You need ten minutes, a camera with a zoom or a choice of lenses (a phone can do every step except the second, since its aperture is fixed), a small object such as a mug, and a background with some small highlights, such as leaves in sun or a string of lights. Keep yourself about 1 m from the mug throughout steps 1 to 3.

1. Put the mug 30 cm in front of the background. Frame it to fill about a third of the picture at your widest aperture and shoot. This is your reference.
2. Close the aperture by two stops (for example f/2.8 to f/5.6) and shoot again from the same place.
3. Go back to the widest aperture and move the mug so it sits 5 m or more in front of the same background. Reframe to the same size and shoot.
4. Put the mug back 30 cm from the background. If you have a zoom, go to its longest end at its widest aperture, step back until the mug is the same size as in step 1, and shoot.

Judge the results side by side at the same size. Measure the width of one blurred highlight against the width of the mug in each frame. Using the rules on this page, predict which change made the biggest difference before you look. With these distances the background multiplier goes from about 0.23 to about 0.83, so moving the mug should make the highlights more than three times larger, while two stops only halves them: the distance change should win. Then look at the highlights themselves: round or polygon, smooth or rimmed, and decide whether the stopped-down frame looks better or worse to you.

Bokeh questions

What f-stop gives the best bokeh?

The widest aperture gives the most blur. Many lenses give rounder discs at the frame edges one stop down, because that reduces cat’s eyes while curved blades still form a near circle. Try both and compare corners.

Why are my bokeh highlights hexagons?

You stopped down, and your lens has six aperture blades, which close into a hexagon that every blurred light copies. Open to the widest aperture for round discs, or use a lens with more or curved blades if you need to stop down.

Do I need a full frame camera for good bokeh?

No. At the same framing and f-number a crop sensor gives about two thirds of the blur on a 1.5x body, which you can make up with a faster lens, a longer focal length or more distance behind the subject. The character of the blur depends on the lens, not the sensor.

Why does my phone blur look different from my camera’s?

Your phone’s lens opening is only a few millimeters wide, so it records almost no optical blur at normal distances. Portrait mode adds blur in software from a depth guess, which is why edges like hair can look cut out.

Can a background be too blurred?

Yes, when the place is part of the story. If the background explains where the person is or what they do, stop down or move closer to it so it stays recognizable while still softer than the subject.

Want to check what stuck? The bokeh and lens rendering quiz asks about cat’s eyes, aberrations and background quality.